Well completion



B. F. BIRDwELl. TAL 2,894,584

July 14, 1959 WELL COMPLETION 2 sheets-*sheet 1 Fiied Dec. 24, 1956NNI..

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United States Patent O f WELL CGMPLETION Bertie F. Birdwell, Austin, andGerald G. Priest and lBryan E. Morgan, Houston, Tex., assgnors, by mesneassignments, to Jersey Production 'Research Company, Tulsa, Okla., acorporation of Delaware Application December 24, 1956, Serial No.630,266 4 Claims. (Cl. -166--42)y The present invention is directed to amethod for completing oil and gas wells. More particularly, theinvention is directed to a method for completing oil and gas Wells inwhich a drilling uid or mud is used to control the well. In its moreparticular aspects, the invention is directed to a method for completingan oil or gas well in which a column of drilling uid is maintained in acasing to control the well.

Current practice when completing wells, such as oil and gas wells,through perforated casings is to have drilling fluids, such as mud, saltWater, water, or oil, in the well casing and to perforate the casingwith bullet, shaped charge, chemical or punch-type perforators. When thepressure of a formation traversed by the well exceeds the hydrostaticpressure of a column of oil or water at the Vcompletion depth, it iscustomary to use weighted salt water or normal drilling mud having adensity great enough to exceed formation pressure in order to controlthe well while perforating the casing and performing other routinecompletion operations. In the case of a well filled with drilling mudwhen the casing is perforated, the drilling mud flows into theperforations because of the pressure differential existing between theinterior of the casing and the formation. The perforations are therebypartially or completely plugged with mud and this plugging is aggravatedby the heat and instantaneous pressure evolved by the propellant powderin the case of bullet perforators and the high explosive in the case ofthe jet or shaped charge perforators. Where chemical or punchtypeperforators are employed, it is'not uncommon for the drilling mud tolose water rapidly to the formation resulting in the drilling mudbecoming dehydrated and forming plugs. Data are available which indicatethat such plugs whether formed by dehydration of the drilling mud byheat, and/ or pressure or by loss of Water to the formation arediflicult to remove by subsequent flow from the formation into the wellbore and that the productivity of a perforated interval in a producingformation is significantly reduced. Field completion attempts of wellsindicate that such plugging of the perforations may cause formations tobe tested as being non-productive and thereby condemned when actuallythe formation may contain economically producible oil or gas. Thus it isclear that the problem of plugging of perforations is serious and is asource of expense in well completions and of erroneous conclusions inexploratory work which may cause major hydrocarbon reserves to remainundiscovered.

Another problem which exists in perforating wells is that it isnecessary to provide control of the well during perforations. This isaccordingly accomplished by maintaining a hydrostatic column whichexerts a pressure greater than the formation pressure exposed when thecasing is perforated. However, to provide a column having a sufficienthydrostatic pressure, it is necessary to add 2,894,584 Patented July 14,1959 HCC weighting agents such as barites, sand, and other solid heaI/ymaterials to the fluid column maintained in the We As it has becomenecessary to drill deeper and deeper wells in search forpetroleum-producing formations, the temperatures encountered in thesedeeper wells have increased to an extent that difficulties have beenencountered. For example, the fluids which heretofore have been used inwells become unstable and tend to lose their properties at the hightemperatures of the order of 200 to 250 F., which may be encountered.For example, emulsions which may be used as completion fluids may becomeunstable and resolve intov their component parts. It is, therefore,desirable to provide a heat-stable emulsion which will maintain andpreserve its characteristics at high temperatures encountered in deepWells.

The high temperatures may be encountered in Wells ranging from 10,000 to25,000' in depth with a usual operation being performed at from about14,000' to about 18,000'. High well temperatures may be encountered atlesser depths, for example, from 6,000' to about 14,000', depending onthe area where the operations are being conducted.

In accordance with the present invention, the plugging of perforationsin well casing in which a column of drilling uid or mud is maintained tocontrol the well is eliminated by providing in the well casing adjacentthe producing formation a body of a thermally stable emulsion, whicheffectively removes, displaces, or excludes the drilling fluid from thatzone and allows perforations to be made in the casing without damagingthe formation by contamination.

The present invention may, therefore, be briefly described as involvingthe placement of an emulsion of an oily and aqueous medium containing asoluble weighting agent dissolved in one of the components of theemulsion, the emulsion being characterized by having a low fluid lossinto the formation, having the property of displacing or excludingdrilling uid from the region of the casing to be perforated or from thesubsurface earth interval to be treated. The particular emulsion is aheat-stable emulsion in which an emulsifying agent selected from thealkali metal salts of purified lignin sulfonic acids containing fromabout 3% to about 33% by Weight of sulfonate groups and from theammonium and alkali metal salts of lignin sulfonic acids containing fromabout 38% to about 57% lignin sulfonic acid groups is employed.

Another problem exists in well recompletion and servicing operations inthat, heretofore, existing perforations in the wall of a well bore or awell casing penetrating into hydnocarbon-productive formationsfrequently were contaminated or damaged by conventional well fluids orWell completion uids while an operation such as treating, sealing orcementing, perforating, fracturing, and the like was carried on orperformed elsewhere in the well such as in a vertically spaced partzo-ne. Heretofore,

there had been no satisfactory way of preventing damage to the existingperforated formation.

In accordance with the present invention, it has been found that suchdamage may be eliminated by placing a body of an emulsion having a lowfluid loss in contact with the perforations or perforated formationwhile conducting or performing operations elsewhere in the well. Hence,the present invention also contemplates the feature of protecting orblanketing selected intervals or zones in the well While reconrpletion,servicing, sealing, or treating operations are conducted in the welleither in a zone or intervalk vertically removed from theemulsionprotected zone or in the emulsion-protected zone.

The emulsion employed in the practice of the present invention is usedin the sense of the emulsions described in Sutheimns Introduction toEmuls1ons, Chemical Publishing Company, Inc., Brooklyn, NewYork, 1947,

- page l, where an emulsion is described as followsz.

Emulsions are intimate mixtures .of two immiscible liquids, one of thembeing dispersed in the other 1n the form. of iine droplets. I

The emulsion of the present invention contains, dissolved in one of thecomponents of the emulsion, a welghting agent Whichis soluble in one ofthe components.

The weighting agent may be soluble either in the aqueous phase or theoily phase ofthe emulsion. For example,

Weighting agent.

puried uniform pine wood lignin is obtained as a byvproduct of pulpingwood chips with a caustic solution to separate and recover the purelignin, which is then sulthe by-products of wood pulping by thesulteprocess the water phase may contain a water-soluble, inorganic fThe oily phase may suitably be a hydrocarbon, such n as crude petroleumand fractions thereof, such as gasoline, kerosene, gas oil, dieseloil,andthe like. Other carbons, such as carbon tetrachloride, and the like,ma form all or part of the oily phase.

The emulsion may either be heavier or lighter than the drilling fluidand suitably may have a density in pounds per gallon in the rangefromabout 7 to about 18 pounds per gallon. The emulsion where lighterthan the drilling fluid may have a suitable viscosity sumcient todisplace the drilling mud and to prevent displacement thereof by thedrilling mud. For example, the viscosity of the emulsion replacing thedrilling mud may range from about l() to about4000 centipoises at 60 F.

The emulsion of the present invention is suitably formed by employing anemulisfying agent of the type known as the Polyfons and the Orzans. ThePolyfons are a series of surface-active-chemicals formed from. purifiedlignin.

- These surface-active agents may be the alkali metal salts such assodium, potassium, and lithium of lignin sulfonic acid. Thecommerciallyk available Polyfons are sodium lignosulfonates and may beldentied as follows:

Grades Percent Sodium Sullonate Groups 2.9 5. s 1c. s 19. 7 26.9 324 shydrocarbonaceous materials `or derivatives of hydro-k my using anammonia base. The Orzans contain from. about 20% to about 40% by weight`of ash land contain varying amounts of sugars. In this process Woodchips consisting of about 90% western `hemlock and 10% white r areplaced into a digester containing ammonium bisulfite and excess sulfurdioxide. The mixturek is cooked for about 8 hours at a temperature ofabout 290-300 F., while a pressure of about 70 to 80 pounds per squareinch is maintained within the digester. After the cooking period, themixture is filtered tokseparate the wood pulp from` i the bisulfteliquor.

Orzan A `is obtainedby concentrating the liquor by evaporation to aboutsolids, and then spray-drying the concentrated liquor. Orzan A,therefore, is an unaltered by-product of the pulping process containingammonium lignin sulfonate and wood sugars.

- Orzan Sis a sodium salt of lignin sulfonic acid and is obtained byadjusting the concentrated ammonium bisulfite liquor to pH 7.0-7.5 withsodium hydroxide. At a pH of 7.0-7.5 the excess ammonia is driven offand the concentrated liquor isspray-dried to obtain a free flowingpowder.

The Orzans AHO, AHI, AH2, and AH3 are made by partiallypolynierizingthelignin sulfonate units present kin Orzan A, increasing the averagemolecularweight from about 10,000 to about 40,000. The member havingthehighest molecular weight is Orzan AH3. 40

A complete description of methods used in the isolation of lignins andthe various lignin sulfonates` by the kraft, soda and sulite processeswill be found in the work by Ott, Spurlin, and Graflin, entitledCellulose and Cellulose Derivatives, lnterscience Publishers, Inc., NewYork, second edition, part 2, pages 524 to 545.

The by-products from this process are ammonium lignin sulfonates andsugars, `occurring in a `fixed proportion. The Orzans available in theindustry and emloyed in the present invention have a composition asshown in the following table:

TABLE I A comparison of the chemical composition of the various OrzansConstituent Analysis-Percent Total Solids Trade Dess Type of Compoundignation Lignin Reducing Available Sulfated Sulfonic Sugar AmmoniaSulfate Ash Ash Acids Orzan-A. Ammonium Lignin Sulfonatc 16. 7 2. 8 1.62.0 21. l Orzan-S Sodium Lignin Sulfonatc 40 10. 6 0.2 1.69 23.0 18. 5Orzan-AI-l0 Polymcrized Ammonium Lignin 55. 2 12. 9 2. 58 1. 52 6. 5 21.3

Sulonatc (Orzan A). Oman-AHL do 55. 5 10. 7 2. 58 l 55 S. 3 21. 4OrZan-AI-I2 .d0 55. 8 9. 5 2. G5 l 57 8.3 22. 2 Orzan-AH3 .do 56. 7 9. 02. i5 l 60 7. 7 22. 4 Orzan-SS Sodium Lignin Sulfonatc 38. 4 0.0 0.0041.3

The extent of sulfonation of the Polyfons is controlled to form theintermediate components having the degree To forml the Polyfons, atedwith them. By processing the ammonium lignin of sulfcnation indicatedbefore.

Thus, it can be seen that the Orzans vary in their degree ofsulfonation` and lthe amount of sugars associ- In a word, the Polyfonsare the alkali sulfonates with sodium" hydroxide, it is possible toforni the alkali metal salt which is substantially free of sugar. Thereare many water-soluble, linorganic Weighting agents which find use inthe practice of the present in- TABLE Il Water soluble inorganiccompounds suitable as weighting agents Specific Name Formula GravityA1Bra 01 A1013 44 A113 98 NHrBr 33 NHA 51 NHrNOa 72 (NHmHPOl 62 SbCla 14SbFa 38 B8,(C2H3Oz)z 47 78 Cadmium iod1de Cadmium nitrate tetrahydrCadmium sulfate heptahydrate. Calcium bromate nionohydrate. Calciumbromide.

Cupric bromate Oupric bromide Ferrous brom' e. Ferrous chlorid Lithiumiodide Magnesium bromid Magnesium iodide. Manganese bromide Manganesechloride tetrahydrat iodide Zinc sulfate CdBlq 2 Cd(C10a)i 3 CdCln 05C6112 67 CCKNOQMAHQO 45 CdS 04.715120 48 CBL(BIO3)2 2H2O 33 CaBrz 35Cach C212 96 CMNOSM 35 C11(Br03)2.6H3O 58 CuBra 2- 8 CuClz 3- 05C11(NO3)2.6H20 2. 07 neon 2- 81 Fe(N0a)a.6H2O 1. 68 Fez(SO4)a.9H2O 2. 1FeBri 4. 64 FeCla 2. 70 Pb(C3H3O2)z.3HgO 2. 55 Pb(C10s)i.HzO 4. 04 PMN03). 4. 53 LiBr 3. 46 LiI 4. 06 MgBrz 8. 72 MgIn 4. MnBrg 4. 39MnCliAHzO 2- 01 Mula 5- 01 NiBri 4- 64 Ni(NOs)i.6H2O 2 05 KCzHaOn 1- 815,00, 2. 2e KF 2. 48 KI 3. 13 KNOz 1 92 K3PO4 2. 56 NEHSOA 2. 74 NaBr3. 20 NaClOx 2. 49 NaCl 2. 16 NaOH k2. 13 N aI 3. 67 NaNO; 2. 26 aNOz 2.17 NaHaP 04.2H20 1. 91 ZnBra 2, 56 ZnClg 2. 91 ZIlIn 4. 66ZI\(NO3)2.6H2O 2. 05 ZI1S04 3. 74

There are many oil-soluble organic Weighting agents which are soluble inthe oily phase of the emulsion ernployed in the practice of the presentinvention. The oilsoluble organic yweighting agents suitably have aspecific gravity in the range Ifrom about 1.2 to about 4. vThese organicweighting agents are illustrated in the following table:

TABLE III Organic weighting agents Name Formula Specific Gravitym-Aminobenzoic acid. NHgCHrCO 0H 1. 511 CH3(CH2)3CH2B1' 1. 218 (CHmOH(CHmBr. 1. 22 (CHQZC (Br) 02H5- 1. 216 C 1. 26 1. 51 1. 515 1. 507 1.471 1. 52A 1. 25 1. 438 1. 54 CiH101N 1. 66 CH5CHIBI'2 1 51 Benzene hexachloride.

Benzoic acid 89 66 Benzanilide- 1. 31 Benzainide.. 1. 34 Benzylbromde 1.44 Beuzylodide.- 1. 73 Bromal BraCCHO 2. 665 p-Bromoacetanilide..BrC5H4NHCOCHa- 1.77 Bromoacetophenone CaH5COCH2Br 1.65p-Bromoaniline. 1. Bromobenzene- 1. 495 Bromoiodobeuzene 2. 257Bromoiodoethane (1,1) 2. 45 1,2Bromoiodoetliane 2. 52 Bromoiodomethane2. 96 Bromonaphthalene 1. 605 Bromosuccinic acid 2 07 Bromatoluene 1.422 Broniotoluene gm) 1.41 Bromotoluene p) 1.39 Brnmnfnrm C 2. 89Butyliodide 1. 617 Chlorobromobenzene 1. 63 Chlorodibroiiioethane 2. 3Chlorodiiodomethane CICH 3.17 Chlorodiiodobenzene-- 1. Chloroiodoethane2.1 Chiorotetrabromoethane. 3. 4 Chlorotribromoethane..- 2. 6Chlorotribromomethane.-. 2. 7 Pentabroinoethane 3. 4 Tetrabroinoethaiie(sym) 2. 96 Iodoform-. 4. 0 Ethylene Dibromide 2. 17 CarbonTetrachloride CO1 1.595 Dichlorobromomethane. 2. 01Dichlorodibromoethane ClzCHCHBrL.-- 2.39 Dichlorotribromoethane.--Br2CClCHBrCL. 2.62 Dilnorobroinoethane F2CHCH2Br 1.82Difluorodibromoethane BrzCHCHFg 2.31 Peruoro-n-heptane CvFw 1.73Prflnorotrimethylpen- CgFrg 1.80

ane. Peruoro(O-dimethy1 CBFN 1. 86

cyclohexane) Tritluoroethanol Peruo- (n-CrFmO 1.71

rodibutylether. Periiuorodiamylether (i1-05111020 1.78Perilriliorodimethyhexyla- CaFnN(CF3)2 1. 82

m e. Pert'luorodipropylethyla- (ri-CaF-MNCRFL 1. 79

mine. Perfluorotripropylamine... (n-CaFgN 1. 82 Peruorotetraethylethy-(CzFmNC FgCFgN(C;F5) 1. 86

lene diamine. Pertluorotributylamina... (n-C4F9)3N 1. 86Periluorotrihexylamine.. nF1s)sN.. 1.93 Trichloroethylene ClCHCCl2 1.47Periuorodihexylether (ii-05111920 1.81

The emulsion employed 1n the present invention will suitably consistessentially of from about 5% to about 95% by Volume of Water with apreferred range from about 20% to about 80% by volume of water, froma'bout 5% to about 95% of oil with a preferred range from about 20% to8O volume percent of oil, and an emfulsifying agent of the typeillustrated in an amount in the range from about 0.5 to about grams per100 ml. of the external phase of the emulsion. j

The weight percent of the inorganic weighting agent or salt dissolved inthe aqueous or water phase will range from 1% up to about saturation,Iwhile the weight percent of organic compound or weighting agentdissolved in the oil phase will range from .1% up to about saturation.

It is contemplated that weighting agents may be present in both the oilyand aqueous phases of the emulsions. However, conditions may exist wherethe weighting agent is present in only one phase of the emulsion.

The presentl invention will be further illustrated by reference to thedrawing, in which:

Figs. l to 6, inclusive, represent a stepwise operation in accordancewith the invention; and

Figs. 7 to 11, inclusive, represent another mode of practicing ltheinvention.

Referring to the drawing in which identical numerals will be employed todesignate identical parts, and particularly to Figs. 1 to 6, numeral 11designates a well drilled from the earths surface, not shown, topenetrate a plurality of subsurface earth intervals 12, 13 and 14. Thewell is lined `with a well casing 15, which may ybe cemented in placewith cement 16. The well casing 15 and the cement 16 may be perforatedin the earth interval 14 to form perforations 17 to allow communicationbetween the formation or zone 14 and the interior of the casing 15 toproduce, for example, oil, gas and other desirable earth minerals. Atubing 18 may be placed in the casing 15 with its lower end 19immediately above the plurality of subsurface earth intervals, sands,zones, strata, horizons, or formations 12, 13 and 14. It may be assumedfor purposes of this description that the intervals 12 and 14 may beproductive of hydrocarbons, while the interval 13 may be non-productive.In the showing of Fig. 1 the well has been drilled and contains drillingfluid or other fluid which may be used for control, such as salt waterindicated by the numeral 20.

In Fig. 2, it is desirable to perform an operation in the well, but yetitis also desirable to protect the perforations 17 against damage. Forexample, if mud were allowed to come into contact with the perforations17, damage to the formation or interval 14 might occur which couldeffectively prevent production of hydrocarbons from the zone 14. It maybe assumed for purposes of this description that it is desirable toperform a cementing operation to prevent communication from back of thecasing with the perforations 17 from the interval either 12 or 13. Tothis end a tubing extension member, such as 21, may be lowered on asuitable wire line, not shown, and located adjacent the lower end 19 ofthe-tubing 18. The tubing extension 21 may suitably be landed, anchored,or supported in the lower end 19 in asuitable landing nipple or othersupporting means, such as 22. By anchoring and sealing the extensionmember 21 in the lower end 19 of the tubing 18, the effective. length ofthe tubing 18 is increased. A body of emulsion, such as 23, then may beplaced adjacent the perforations 17 displacing the fluid 20 up theannulus A between the tubing 18 land the casing 15. It will be seen byplacing an emulsion of the type indicated before adjacent theperforations 17, the perforations 17 are effectively blanketed andprotected. T here after, the tubing extension 21 is removed from thetubing 18 by attaching a wire line, not shown, to -the fishing head 24and retrieving same from the tubing. A-s shown in Fig. 3, a gunperforator 25, which may be of the Shaped charge or bullet type, islowered on the wire line `26 to perforate the interval 12. Theperforator 25 may be one of the chemical or mechanical types, butpreferably is a bullet gun or a shape charge gun. The

perforator is then operated or fired to form perforations 27 in thecasing 15, cement 16, and to penetrate the interval 12. Thereafter, theperforator 25 is retrieved from the tubing 18 by wire line 26and a bodyof cement 28 is then placed adjacent the perforations 27A and squeezedoutwardly to fill the perforations 27 and any channels between the wallof the wellbore 11 and the casing 15 to prevent communication with theperforations` 17. After the cement has been squeezed by imposingpressure on thebody 28, the excess cement may be removed by employing atubing extension member, such as 21, and to remove the excess cementwhich may be of a modified type having a low fluid loss and whichremains fluid for a suicient length of -time to allow circulation of thecement out. A :suitable modified cement is described in the patent toSalathiel, U.S. Patent No. 2,582,459. After the fluid cement has beenremoved, the perforations 27 are effectively sealed, as indicated, andit becomes desirable to remove the body of emulsion 23. This is alsoaccomplished by placing a tubular extension member, such as 21a, in thelanding nipple 22 and circulating the emulsion out as indicated by thearrows shown in Fig. 5 using a suitable circulating fluid. Thereafter onremoval of the emulsion, pro duction may again be had from the interval14, which has been protected during the operations from damage bycontact with fluids in the well. This flow is shown las indicated by thearrows. The emulsion may be flowed outwardly without the use of a tubingextension by suitlably swabbing the well.

Referring now to Figs. 7 to ll, 11 designates a well drilled from theearths surface, not shown, to penetrate a plurality of subsurface earthintervals 12, 13 and 14. The well is lined with a Iwell casing 15, whichis cemented in place with cement 16. The 'well casing 15 and the cement16 has been perforated previously in the earth interval 14 to formperforations 17 to allow communication between the formation or zone 14and the interior of the casing 15 lto produce, for example, oil, gas andother desirable earth minerals. A tubing 18 is in the casing 15 with itslower end 19 immediately 'above the perforations 17. This condition isillustrated i in Fig. 7.

For purposes of explanation, it is desirable to protect theseperforations 17 opposite the formation 14 while new perforations are tobe made in formation 12. Salt water 20 is pumped into tubing 18 untilthe 'annulus 30 is either filled with salt water or` lthe hydrostaticcolumn becomes balanced with the formation pressure in the formation 14.This step of the operation is illustrated in Fig. 8.

A predetermined quantity of emulsion, `according to this invention, ispumped through tubing 18 until the emulsion yreaches the lower end ofthe tubing 19. At this point, the casing side is closed at the surfaceand the emulsion in tubing 18 is displaced by' pumping salt water intotubing 18 until the emulsion 23 contacts the face of formation 14through perforations 17. Further displacement of the emulsion is madelto cover formations 12, 13 and 14, :as illustrated in Fig. 9.

Tubing 18 is withdrawn from the -well and perforator 25 is lowered intothe well opposite formation 12 and tired to make perforations 31, asillustrated in Fig. 10.

The perforator is removed from the well fand tubing 18 with packer 32 islowered into the well. The packer 32 is set as shown in Fig. 11 toaccomplish dual completion of the well. Hydrocarbon production fromformation 12 through perforations 31 is directed into the annulusbetween the tubing 18 and the casing 15 Iwhile production ofhydrocarbons from formation 14 through perforations 17 occurs throughthe inside of tubing 18.

In order to illustrate the invention further, la number of compositionswere prepared in `accordance with `the present invention. Thesecompositions `are set out in the following table:

TABLE IV Composition and properties of emulsions containing calciumchloride and different solids Composition of Emulsion Composition ofAqueous Phase Oil Phase EmUlSier Sample No. External Aqueous PhasepfPhase, Solids 'Fmnlsmn C9013, g./1001Il1. Percent Wt., Identity Vol.,Identity External Identity g./1100 Percent Percent Phase 60 2.0 40Diesel 0i1 40 Polyon 0 2.0 60 d 2.0 40 do 40 Polyl'on R 2.0 60 d 2.0 40PolyfonT 2.0 60 do 2.0 PolyionE 2.0 60 d0 2.0 d0- 3.0 e do- 2.o 1-0 60 d2.0 0-5 60 1.0 2.0 60 0.5 2.0 60 d0 2.0 2.0

Polyvinyl alcohol- 1. 0 60 Pozrnix-MO 2.0 Polyon H 2.0

Polyvnyl alcohoL.. 0.5 Ox- 8 1.0A 60 Pozmix-MO 2.0 Polyfon H 2.0 TritonXGL... 1. 0 60 do 2.0 PolyfonH 2.0 Pluronic F68 1. 0 60 Pozmix 2.0Polyfon H 2.0 60 IndulinA 2.0 40 2.0 60 Calcium Hydroxide- 2.0 40 2-0 60d0 1.0 40 2.0 so do- 0.5 40 2-0 so geioiay 2.o 4o o 5o do 2.o 40 do 2.0

Polyvinyl alcohoL-. 0. 5 do 1.o do 2-0 0.5 40 do 20 0.25 40 do 2.0 0,2540 do 1.0 0.25 40 do 05 4o do 2.0 4o do 2-0 40 do 2-0 40 do L0 40 do 1-04o do 2.0 40 2.0

40 2.0 e 40 1.0 2.0 40 2.0 2.0 40 2.0 2.0 40 2.0 2.0 40 2.0 2.0 40 3.02.0 40 1.0 -do 2.0 40 0.5 60 Calcium Carbonate. 1.0 40 2.0 60 ZeogelClay 2.0 40 2.0 60 do 2.0 40 do 60 Aquagel Clay 2.0 40 do 2-0 eo do 2.04o d5 2g l. 60 Xact Clay 2,0 40 do 20 so do 2.0 40 do 2-(l) 1. o0 4o d02.0

' TABLE IV-Continued on following page.

It may be seen from an examination of the data in the immediatelypreceding table that these emulsions have very low iluid losses at roomtemperatures and after aging at 250 F. By vway of explanation, emulsionshaving a fluid loss above 40 ml. in 30 minutes at room temperature afterthe sample has been aged for 24 hours at 250 F., or those having a fluidloss above 80 ml. in 30 minutes at a ltest temperature of 250 F., may beconsidered unsatisfactory as well completion fluids under someconditions, since they may not remain in place to protect the exposedface of -a subsurface interval.

It is to be particularly noted that the Polyfonand Oman-containingemulsions are particularly suitable after both atmospheric and elevatedtemperature aging and, therefore, are useful as completion and servicingiluids in wells of normal and elevated temperatures.

In the composition of the present invention, it is desirable vtostabilize the emulsion, and this may suitably be done by employingsuitable stabilizing agents which may be of dispersible solid materialand which may be identified as Pozmix, Pozmix 140, line, Xact clay.Other stabilizing `agents such as polyvinyl alcohol in admixture withthe Pozmix and the lime, Zeogel clay and calcium hydroxide may also beused. These several dispersible solids are particularly desirable at theelevated temperatures encountered in deep Wells and may be used inamounts from about 0.5 gram to about 3.0 grams per 100 m1. of theaqueous phase. Y

The compositions of the present invention are quite useful asperforating fluids and well completion iluids and have the property ofprotecting the formation and preventing damage of the formation byeliminating contact with contaminating bodies. For example, when thecomposition of the present invention is used as a perforation uid, thepermeability of the formation is not damaged and flow is readilyobtained therefrom. Furthermore, the composition of the presentinvention allows formations -to be protected While conducting operationsin the well displaced from the protected formation.

While the invention specifically contemplates its use and application toperforating, servicing, and completion operations in cased wells, it isunderstood that these applications and uses are given by way ofillustration and not by way of limitation. Thus, the present inventionTABLE IV-Continued Composition and properties of emulsions containingcalcium' chloride and different solids-Continued Properties of EmulsionAPI Fluid Loss Sample No.

Density, At Room Temperature At Elevated Tempera- Iii/gal.` ture bBefore Aging, After Aging,n F. mlt/O IDL/30 min. IDL/30 min. mm.

15 9. 6 11.0 13.8 16-- 9.6 11.0-.- 16. 17-- 9. 6 l2.2 18. 18- 9.6 9.8...ll. 19. 9. 6 9.2. 16. 20- 9.6 17.0. 26. 21. 9. 6 21.0- 30. 22- 9.6 14.823. 9.6 15.0 24- 9. 6 16.8 25- 9.6 5.4- 26. 9. 6 8.2. 27, 9. 6 10.2--28- e. o 17.0.- 29- 9. o 25.0-- 30- 9. 6 12.4. 31- 9. 6 12.0-. 32- 9,612.0-. 33- 9.6 9.0... 2in41n1r1- 34- 9. 6 23.0...- 25 in 15 min, 35- 9.6 25 in 10 mm. 25 in 10 min.. 3G- 9.o 25111 12 man 25 in 1 min- 37- 9. 616.8 38. 9. 6 25 in 10 mim 25 in 2 min. 39- 9.6 25 in 6 min. 25 in 3min. 40 9. 6 16 4l 9.6 1l.8 42 9. 6 11.2-- 43 9. 6 16.4. 44 9. 6 18.4.-45 9. 6 15.6. 46 9. 6 14.0-.-- 47 9. 2 17.0. 48.- 9. 2 21.0- 53.- 9. 613.8- 25 1n 12 min 54-- 9. 6 11.2- 25 in 8 min 55-- 9. 6 9.8- 0.2 56.-9. 6 13.0. 57.- 9.6 11.2. 58 9. 6 22.0- 59 9. 6 35.0. 60.. 9. 6 15.2-61-- 9. 6 13.6. 16.0. 62.. 9.6 1.6-. 25 in. 2 min. 63-- 9.6 13.6. 16.464.. 9. 6 21.4- 65-- 9. 6 20.4. 66-- 9. 6 6.0.- 67 9. 6 19.4

n Sample aged in a closed cylinder at 250 F. for 24 hours or longer,then cooled to room temperature und tested. h Tested in a Baroidhigh-temperature lter press; result doubled to convert it to regular APIbasis.

is applicable to fracturing of subsurface earth intervals; the inventionmay also be used in treatment of a selected zone pierced by a well witha chemical to improve the characteristics of a selected zone, with theemulsion being used to protect or blanket another selected zone toprevent damage thereto or to prevent change of character of theprotected zone.

The present invention may suitably be used in dual or multiplecompletions where there may be iluid communication between verticallyspaced apart zones, the improved emulsion being used to protect one zonewhile a remedial or sealing operation is conducted in the other Zone.

It is also important in the present invention that, whenever operationsare conducted in a well, the emulsion is the first uid, other than thedesired mineral, such as oil and/or gas, which contacts the exposedperforations. Thus, it is specifically contemplated that the emulsionmay be used to contact the perforations and protect same following whichdrilling uid, mud, salt Water, and the like may then be ilowed past theprotected perforations which may contain the emulsion. The emulsion thusprotects the clean perforation, without damaging the earth interval andwithout losing iluid thereto.

It is also within the purview of the invention to conduct all workoveroperations using the present invention 50 with the improved emulsionprotecting exposed faces of earth intervals undergoing servicing orreworking. However, the emulsions of the present invention may be usedwith other Well fluids so long as the exposed interval is protectedagainst damage by contact with the detrimental lluid.

The nature and objects of the present invention having been completelydescribed and illustrated, what We Wish to claim as new and useful andto secure by Letters Patent is:

1. A method for completing and servicing a Well containing drillingfluid in which high temperatures of the order of 200 to 250 F. areencountered which cornprises placing in said well an emulsion,containing from about 5% to about 95% by volume of an aqueous medium,from about 5% to about 95% by volume of an oily medium, a Weightingagent in an amount within the range between about 1% by Weight to aboutsaturation dissolved in at least one of said media, and an emulsifyingagent selected from the alkali metal salts of puried lignin sulfonicacids, in which sugars, hemicelluloses, and other degradation productshave been removed, containing from about 3% to about 33% by weightsnlfonate groups and ammonium and alkali metal salts of lignin sulfonicacids containing from about 38% to about 57% lignin sulfonic acid groupsin an amount in the range between 0.2 and about 20 grams per 100 ml. ofthe external phase of the emulsion, said emulsion having a density inthe range from about 7 to about 18 pounds per gallon and different fromthat of the drilling fluid and a viscosity at 60 F. in the range fromabout 10 to about 4,000 centipoises, displacing a portion of saiddrilling iluid in said well from a point adjacent a selected subsurfaceinterval penetrated by said Well, contacting an exposed face of saidselected subsurface earth interval at said point with said emulsion toprotect said exposed face against contamination with said drilling fluidsuch that the emulsion is the irst uid other than hydrocarbons whichcontacts said exposed face, performing an operation in said Well, saidemulsion being subjected to said temperatures of the order of 200 to 250F. in said well and being maintained in contact with said exposed faceWhile said operation is being performed, said emulsion beingcharacterized by having a low ltration rate and by not damaging saidearth interval, said emulsion being stable at said temperature, removingsaid emulsion from said exposed face after completion of said operation,and then producing hydrocarbons from said exposed face.

2. A method in accordance With claim 1 in which the operation in saidwell comprises the placing and operation of a perforator in saidemulsion to penetrate the selected earth interval.

3. A Well completion composition which comprises an emulsion containingfrom about 5% to about 95% by volume of an aqueous medium, from -about5% to about by volume of an oily medium, a weighting agent in amountWithin the range from about 1% by Weight to about saturation dissolvedin at least one of said media, and an emulsifying agent in an amount ina range between about 0.2 and about 2O grams per 100 ml. of the externalphase of the emulsion selected from the group consisting of alkali metalsalts of purified lignin sulfonic acids, in which sugars,hemicelluloses, and other degradation products have been removed,containing from about 3% to about 33% by weight sulfonate groups andammonium and alkali metal salts of lignin sulfonic acids containing fromabout 38% to about 57% by Weight lignin sulfonic acid groups, saidemulsion being heat stable at Well temperatures of the order of 200 to250 F.

4. A composition in accordance with claim 3 in which the agent is a highspecic gravity halogenated hydrocarbon `dissolved in the oily phase ofthe emulsion.

References Cited in the le of this patent UNITED STATES PATENTS2,223,397 White Dec. 3, 1940 2,742,426 Brainerd Apr. 17, 1956 2,805,722Morgan et al. Sept. 10, 1957 OTHER REFERENCES Dispersants From SilteLiquor by Salvesen et al. Reproduced from Chemical Industries, August1947.

1. A METHOD FOR COMPLETING AND SERVICING A WELL CONTAINING DRILLING FLUID IN WHICH HIGH TEMPERATURES OF THE ORDER OF 200* TO 250*F. ARE ENCOUNTERED WHICH COMPRISES PLACING IN SAID WELL AN EMULSION, CONTAINING FROM ABOUT 5% TO ABOUT 95% BY VOLUME OF AN AQUEOUS MEDIUM, FROM ABOUT 5% TO ABOUT 95% BY VOLUME OF AN OILY MEDIUM, A WEIGHTING AGENT IN AN AMOUNT WITHIN THE RANGE BETWEEN ABOUT 1% BY WEIGHT TO ABOUT SATURATION DISSOLVED IN AT LEAST ONE OF SAID MEDIA, AND AN EMULSIFYING AGENT SELECTED FROM THE ALKALI METAL SALTS OF PURIFIED LIGNIN SULFONIC ACIDS, IN WHICH SUGARS, HEMICELLULOSES, AND OTHER DEGRADATION PRODUCTS HAVE BEEN REMOVED, CONTAINING FROM ABOUT 3% TO ABOUT 33% BY WEIGHT SULFONATE GROUPS AND AMMONIUM AND ALKALI METAL SALTS OF LIGNIN SULFONIC ACIDS CONTAINING FROM ABOUT 38% TO ABOUT 57% LIGNIN SULFONIC 